Indomethacin promotes browning and brown adipogenesis in both murine and human fat cells

Biofabrication of 3D adipose tissue via assembly of composite stem cell spheroids containing adipo-inductive dual-signal delivery nanofibers

Reconstruction of large 3D tissues based on assembly of micro-sized multi-cellular spheroids has gained attention in tissue engineering. However, formation of 3D adipose tissue from spheroids has been challenging due to the limited adhesion capability and restricted cell mobility of adipocytes in culture media. In this study, we addressed this problem by developing adipo-inductive nanofibers enabling dual delivery of indomethacin and insulin. These nanofibers were introduced into composite spheroids comprising human adipose-derived stem cells (hADSCs). This approach led to a significant enhancement in the formation of uniform lipid droplets, as evidenced by the significantly increased Oil red O-stained area in spheroids incorporating indomethacin and insulin dual delivery nanofibers (56.9 ± 4.6%) compared to the control (15.6 ± 3.5%) with significantly greater gene expression associated with adipogenesis (C/EBPA, PPARG, FABP4, and adiponectin) of hADSCs. Furthermore, we investigated the influence of culture media on the migration and merging of spheroids and observed significant decrease in migration and merging of spheroids in adipogenic differentiation media. Conversely, the presence of adipo-inductive nanofibers promoted spheroid fusion, allowing the formation of macroscopic 3D adipose tissue in the absence of adipogenic supplements while facilitating homogeneous adipogenesis of hADSCs. The approach described here holds promise for the generation of 3D adipose tissue constructs by scaffold-free assembly of stem cell spheroids with potential applications in clinical and organ models.

Unleashing the potential of adipose organoids: A revolutionary approach to combat obesity-related metabolic diseases

Obesity-related metabolic diseases, including obesity, diabetes, hyperlipidemia, and non-alcoholic fatty liver diseases pose a significant threat to health. However, comprehensive pathogenesis exploration and effective therapy development are impeded by the limited availability of human models. Notably, advances in organoid technology enable the generation of adipose organoids that recapitulate structures and functions of native human adipose tissues to investigate mechanisms and develop corresponding treatments for obesity-related metabolic diseases. Here, we review the general principles, sources, and three-dimensional techniques for engineering adipose organoids, along with strategies to promote maturation. We also outline the application of white adipose organoids, primarily for disease modeling and drug screening, and highlight the therapeutic potential of thermogenic beige and brown adipose organoids in promoting weight loss and glucose and lipid metabolic homeostasis. We also discuss the challenges and prospects in the establishment and bench-to-bedside of adipose organoids, as well as their potential applications.

Naringin promotes fat browning mediated by UCP1 activation via the AMPK signaling pathway in 3T3-L1 adipocytes

Induction of the brown adipocyte-like phenotype in white adipocytes (fat browning) is considered a promising therapeutic strategy to treat obesity. Naringin, a citrus flavonoid, has antioxidant, anti-inflammatory, and anticancer activities. We examined the application of naringin as an anti-obesity compound based on an investigation of its induction of fat browning in 3T3-L1 adipocytes. Naringin did not induce lipid accumulation in differentiated 3T3-L1 adipocytes. Additionally, naringin reduced the expression levels of proliferator-activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein alpha (C/EBPα) involved in adipogenesis during lipid metabolism and increased the levels of PPARα and adiponectin involved in fatty acid oxidation. The expression levels of fat browning markers uncoupling protein 1 (UCP1; involved in thermogenesis) and PR domain containing 16 (PRDM16) increased. In addition, naringin treatment resulted in the activation of PPARγ coactivator 1-alpha (PGC-1α), a factor related to UCP1 transcription and mitochondrial biogenesis. Moreover, the expression of beige adipocyte-specific genes such as Cd137, Cited1, Tbx1, and Tmem26 was also induced. The small multi-lipid droplets characteristic of beige adipocytes indicated that naringin treatment increased the levels of all lipolysis markers (hormone-sensitive lipase [HSL], adipose triglyceride lipase [ATGL], perilipin [PLIN], and protein kinase A [PKA]). Adenosine monophosphate-activated protein kinase (AMPK) and UCP1 levels increased by treatment with naringin alone; this was possibly mediated by the stimulation of the AMPK signaling pathway. According to mechanistic studies, naringin activated the thermogenic protein UCP1 via the AMPK signaling pathway. In conclusion, naringin induces fat browning and is a promising therapeutic agent for metabolic disorders based on the regulation of lipid metabolism.

Naringenin, a citrus flavanone, enhances browning and brown adipogenesis: Role of peroxisome proliferator-activated receptor gamma

Identifying functional brown adipose tissue (BAT) has provided new hope for obesity treatment and prevention. Functional BAT includes classical BAT and brown-like adipose tissue converted from white adipose tissue. By promoting thermogenesis (i.e., heat production) via uncoupling protein 1 (UCP1), functional BAT can increase energy expenditure and aid obesity treatment and prevention. Naringenin (NAR) is a flavanone primarily found in citrus fruits. NAR has been reported to decrease body weight, increase energy expenditure in treated mice, and promote browning in human adipocytes. Here, we examined the effects of NAR on 3T3-L1 adipocytes' browning and β-adrenergic agonist isoproterenol (ISO)-stimulated thermogenic activation and classical murine brown adipogenesis. In addition, we demonstrated the signaling pathways and involvement of peroxisome proliferator-activated receptor gamma (PPARγ) in the process. We found that NAR did not increase Ucp1 mRNA expression at the basal (i.e., non-ISO stimulated) condition. Instead, it enhanced Ucp1 and Pgc-1α up-regulation and thermogenesis under ISO-stimulated conditions in 3T3-L1 adipocytes. NAR promoted protein kinase A (PKA) activation and phosphorylation of p38 MAPK downstream of ISO stimulation and activated PPARγ. Pharmacological inhibition of either PKA or p38 and PPARγ knockdown attenuated Ucp1 up-regulation by NAR. Moreover, NAR promoted brown adipogenesis by increasing lipid accumulation, brown marker expression, and thermogenesis in murine brown adipocytes, which was also attenuated by PPARγ knockdown. Together, our results suggest that NAR may promote the development of functional BAT in part through PPARγ activation. NAR's role in combating human obesity warrants further investigation.

Preventing White Adipocyte Browning during Differentiation In Vitro: The Effect of Differentiation Protocols on Metabolic and Mitochondrial Phenotypes

Mitochondrial dysfunction in white adipose tissue is strongly associated with obesity and its metabolic complications, which are important health challenges worldwide. Human adipose-derived stromal/stem cells (hASCs) are a promising tool to investigate the underlying mechanisms of such mitochondrial dysfunction and to subsequently provide knowledge for the development of treatments for obesity-related pathologies. A substantial obstacle in using hASCs is that the key compounds for adipogenic differentiation in vitro increase mitochondrial uncoupling, biogenesis, and activity, which are the signature features of brown adipocytes, thus altering the white adipocyte phenotype towards brown-like cells. Additionally, commonly used protocols for hASC adipogenic differentiation exhibit high variation in their composition of media, and a systematic comparison of their effect on mitochondria is missing. Here, we compared the five widely used adipogenic differentiation protocols for their effect on metabolic and mitochondrial phenotypes to identify a protocol that enables in vitro differentiation of white adipocytes and can more faithfully recapitulate the white adipocyte phenotype observed in human adipose tissue. We developed a workflow that included functional assays and morphological analysis of mitochondria and lipid droplets. We observed that triiodothyronine- or indomethacin-containing media and commercially available adipogenic media induced browning during in vitro differentiation of white adipocytes. However, the differentiation protocol containing 1 μM of the peroxisome proliferator-activated receptor gamma (PPARγ) agonist rosiglitazone prevented the browning effect and would be proposed for adipogenic differentiation protocol for hASCs to induce a white adipocyte phenotype. Preserving the white adipocyte phenotype in vitro is a crucial step for the study of obesity and associated metabolic diseases, adipose tissue pathologies, such as lipodystrophies, possible therapeutic compounds, and basic adipose tissue physiology.